Project Summary There is increasing attention to the need for enhancing the evaluation and communication of the benefits and risks associated with pharmaceutical products, thereby increasing the predictability, transparency and efficiency of pharmaceutical regulatory decision-making. Pursuant to its commitments under the fifth authorization of the Prescription Drug User Fee Act (PDUFA V), FDA must convene two public workshops that address important considerations, from the regulator's perspective, on benefit-risk assessment. For the first workshop, FDA has identified an important opportunity to generate insight that can advance the development of more structured approaches to facilitate the characterization, evaluation and communication of uncertainty that arises in the assessment of benefits and risks. At the request of FDA, an ad hoc committee of the Institute of Medicine (IOM) planned and conducted two one-day public workshops at FDA's White Oak facility to explore systematic and structured approaches to characterize and communicate (a) the sources of uncertainty in the assessment of benefits and risks; and (b) their implications for pharmaceutical regulatory decisions.